Telephone system



Arg-i1 z3, 1940.,

F. LlLL TELEPHONE SYSTEM Filed Oct. 2. 1937 I Go INVENTR, I

FRIEDRICH LILL ATTORNEY.

Patented Apr. 23,l 1940 UNITED s'rATi-:SA

TELEPHONE SYSTEM Friedrich Lill,

Vienna, Austria, assigner to Siemens & Halske Aktiengesellschaft, Wernerwerk, Siemensstadt, near Berlin, Germany Application October 2, 1937, Serial No. 167,056

In Germany October 3, 1936- 22 Claims.

In remote communication systems, and more particularly in telephone systems, arrangements are already known which render the calling con-A dition at subscribers lines inoperative as regards its iniiuence on the connecting devices in the exchange if no switching measures for setting up a. connection are taken at a calling station within a given time after the call initiating impulse has been transmitted. In one arrangement a spe cial disconnecting relay, which is connected to the subscribers line on the interruption of the locking circuit by the quick to release cut-oft relay, is maintained energized by the calling condition and as a result prevents the callingcondition of this line inuencing the connecting devices ofthe exchange. y n y 'Arrangements have also been proposed in which while avoiding a special auxiliary relay anexisting calling condition is rendered inoperative merely by the cooperation of two relays with which the subscriber's line is already provided for other purposes. Thus, for example, by the interrupting of the locking circuit existing during a call for the slow-to-release cut-off relay and the quick-to-release call relay the first is connected to the subscribers lineand is held energized over this. In another arrangement an auxiliary relay provided for a special purpose (operating a meter) causes the calling condition of the subscribers line to be renderedinoperative in cooperation with the combined lineand cut-off relay in the form of a two-stage relay The present invention is based upon the desirability of producing an emcient and simple method of rendering inoperative a calling condition at the subscribers line in systems in which the subscribers lines are not provided with 'any individuall call receiving relays; This is achieved in that when a callis set up between the subscribers line and another line', the cut-off` relay associated with the subscribers line brings a switching means rendering the calling condition of the subscribers line inoperative under the influence-of switching devices arranged in a succeeding portion of the connecting path which characterize the non-performance of switching -measures (impulse transmission for setting .upa call or the replacement of a receiver. for releasing a call) at the calling station. A special switching means or the cut-off relay itself can be used for rendering the calling condition inoperative. In the latter'case the cut-off relay is made aftwo-stage relay which .when completelyl energized prevents the calling condition of Ithe subscribers line exerting any further inuence on the connecting devices of the exchange.

In the case of systems with call nders in which the testing circuit passes over the calling subscribers line the connection of the switching devices which render the calling condition inoperativeto the subscribers line can take place after the setting of the call finder at the portion of the testing circuit leading to the connecting'v devices of the exchange, thereby avoiding any special construction of the connecting devices, for example special wipers in the switches or in the case of relay switches special contacts on the switching through relay.

If the calling condition at the subscribers line is not to be rendered inoperative by the interruption of a locking circuit maintaining the connection because as in the case of subscribers lines without individual line relays there are not two relays with diierent release characteristics available considerable difficulties are involved if the position from which the impulse forrendering the calling condition of a line operative proceeds is separated from the line by a number of selecting stages.

In this case also the invention enablesl the switching means for rendering the calling condition inoperative to be controlled in a particu.

which the subscribers meter'is operated is modied so that the switching means. of the subscribers line which result inrendering its calling condition inoperative can be inuenced over this circuit.

The drawing indicates oneembodimentofthe i invention to which the latter'is not limited.

When the receiver istaken up at the station Tn which has no individual calling relay associated with it in the exchange the start relay An common to the subscribers group energizes in the following circuit: positive; relay An, resistance I, contact 2tI, lead 3, subscribers station Tn, lead 4, contact 5tI, resistance 6 and negative. At contact 1an the start relay R associated with a free iinder link AS-VW is energizedjover:rpositive, contacts 1an, and 822|, relay R. and-.neg- .'ative. At contact 91' the circuit for the rotary magnet Duw of the preselector VW of `the'preselector linkJAS-VW `which is set in readiness is closedz-fnegative, Dvw,`contact vIllpl 'and 9r, interrupter YI I, and positive.

At contact 'l2r the testing circuit is prepared and when a free connecting line which may for .example lead to a. first group selector is found this circuit is completed over winding II and I` PATENT ortica.

larly simple way in that a metering circuit over of relay PI, contact 121-, wiper I3, contact I4, seizing relay C and positive. Relay P| energizes and opens contact |p| and thereby brings the preselector VW to rest and at contact |p| completes the circuit for driving magnet Das of the call finder AS'. By short-,circuiting its own resistance winding I at contact 26p| the seized group selector is guarded against seizure by another preselector.- At contacts 2`|p| and 28p| testing and locking circuits are closed over the Wipers of the call finder.

Before proceeding with the explanation of the switching operations in the preselecting stage it should be mentioned that relay C in the free connecting line which has been found is slowto-energize and when energized closes inter alia its contact I 6c. The vertical magnet HI of the group selector IGW is, however, prevented from energizing in that the bridge relays A and B in the first group selector are energized over an auxiliary bridge in the preselecting stage completed by the testing relay Pl of the preseleetor VW in the following path: negative, relay A, contact I1, wiper 68, contacts |8p|, |911| and 20T, resistance 2|, wiper 22, contact 23, relay B and positive. Relay A opens its contact 24a disposed in series with contact IGc and thereby -prevents relay V2 and the vertical magnet HI from energizing. Contact 25a is closed for purposes which will be explained later.

After relay PI has energized and has closed contact |5fp| the call finder AS hunts for the calling line because its rotary magnet is energized in the following circuit: negative, rotary magnet Das, contacts 29112, |5p| and 91', interrupter and positive. When the calling subscribers line is found the following testing circuit is closed: positive, contact 21pl, winding I of relay P2, contact llr, wiper 30, contacts 3| and 32tI, lead 3, subscribers station T11., lead 4, contact 5tI, resistance -6 and negative. In this testing circuit owing over the subscribers line relay P2 energizes and brings the call finder to rest by opening contact 29112, at contact 33112 switches through the lower switching lead and at contact 34112 completes the following circuit; positive, contact 28pl, winding'II of relay P2, contact 34112, relay VI, Wiper 35, contacts 36 and 31tII, winding I of relay T and negative. In this circuit relays T and VI energize.

Relay VI closes its contact 38v| and then opens its contact 911| thereby opening the auxiliary bridge over contact 201' and resistance 2| and bringing the relays A and B of the first group selector under the influence of the calling subscriber. Through the opening of contact 811| relay R is disconnected and through the closing of contact 390| thexlead from the start contact 1an is switched through to lead 40 leading to the next call finder. Relay R makes a delayed release and switches its contacts 91', ||1', 121' and 201 back to normal.

At the calling subscribers line the cut-off relay T which is a two-stage relay is energized in its' first stage by the current passing over its winding I and thereupon switches all the contacts indicated by the reference I from the rest .position shown into the operated position, consequently contacts 2tI, 5tI and 32tI are opened and contact 4|tI is closed. Through the opening of contact 32tI and the closing of contact-"tI the testing circuit passing over the subscribers line is .switched over. In the portion of the testing circuit leading to the connecting devices of .the exchange the switching means which render inoperative the calling condition at the subscribers line are connected up. The switching means consist of a winding IIA enabling the cut-01T relay T to be completely energized. Naturally a separate auxiliary relay can be provided for the purpose of rendering the calling condition inoperative. I The contacts of relay T bearing the reference II are not inuenced when the relay is energized over its winding I but remain in the rest position shown.

When the calling subscriber transmits numerical impulses for setting up the connecting path these are transmitted to the vertical magnet HI by the closing of contact 24a. The relay V2 disposed in series with the vertical magnet energizes and at contact 42v2 breaks the heating circuit completed at contact 25a over the thermo-relay Thl. The rotary magnet which is not shown is operated in the known way after the termination of the impulse train eecting the vertical setting of the group selector by the release of relay V2 in cooperation with an off-normal contact closed on the first vertical step of the group selector. The group selector now hunts for a free outgoing line in the selected group. On the -first rotary step of the switch the rotary offnormal contact 43w is opened so that the thermorelay Thl can now no longer be operated.

V The case will now be considered in which after the setting of the preselecting devices AS and VW in response to a call initiating impulse the calling subscriber waits too long before operating his dial switch, or the call initiating impulse is falsely produced by a fault in the subscribers line or at the subscribers station. After the energizing of relay A in the first group selector of the circuit closes at contact a for the thermo-relay Thl remains' operative for a prolonged time; negative, vertical magnet Hl winding I of relay V2, contact 43w, thermo-relay Thl, contacts 4202 and 25a and positive. In this circuit neither the vertical magnet H| nor relay V2 (winding I) can energize. The thermo-relay heats up and after the expiry of its heating period closes contact 44th| thereby preparing for the rendering inoperative of the calling condition at the line which has-.seized the first group selector.

'I'he subscribers lines are provided with call meters which are operated by the closing ot contact 60, by a meter stepping device ZIS at definite intervals of time after the closing of contact 45er. Contact 45er is controlled for example by a relay (not shown) which energizes at the moment when the metering commences. The metering circuit passes as follows: negative, meter Z, contact 46, wiper 41, contact 48u11, wiper 43, contacts 50, 45er and 60 and positive. y

The meter stepping device is also provided with special contacts ab, which are closed at definite intervals of time, and serve to render inoperative the calling condition at subscribers' lines. The contacts ab are operated at different times from contact 60 which serves for influencing the meter. The device can be so arranged that the contacts 60 and the contacts ab are always operated alternately or so that the contacts ab are closed once `after contact 60 has been closed a number of times. The switching over of the contacts ab results in switching over the metering circuit. Through the opening of contact ab and the closing of contact Slab, lthe lead of the metering circuit proceeding from wiper 49 is switched over on to wiper of the call finder. At the same time negative potential is connected over contact 52ab.' If now at the moment of operation of the 15 contacts uab, Slab and Hab the thermo relay Thl has become operative on account ofthe rst impulse train not having been transmitted lby the calling subscriber and has closed contact thi the following circuit which operates the cut-oif contacts 3l and litI, winding II of relay T and positive. All the contacts of relay T indicated' by the reference II are now switched over into the operated position, i. e., contact 31t1'I is opened and contacts 55H1 and SGtII are closed. 'I'he result of thisis that the energizing winding of relay T is connected to the subscribers line. Relay T remains completely energized in the circuit over the subscribers line: negative, winding I of relay T, contact SBtII, lead 4, subscribers station Tn, lead 3, contact BBtII and positive. Relays VI and P2 are deenergized by the opening of contact S'ItII and release. Relays 'A and B at the iirst group selector release on account of the opening of contact 33122. The seized switches AS,

VW and IGW are thereby released and can be taken into use for other calls.

Instead of infringing about the energization of relay T in the subscribers line in the second switching stage by the cooperation of the meter stepping device the-same operation can be carried out, for example, by disposing an auxiliary relay in series with relay PI, which only responds to strong current. 'I'his increase in the current .strength can be brought about temporarily by the thermo-relay Thl in that the contact of the latter short-circuits relay C or a resistance disposed in series with the latter. The auxiliary relay can be connected directly to wiper 30 and can thereby enable the armature of'relay T to be fully operated.

The devices, which render the calling condition of a subscribers line inoperative, if switching operations necessary for the further establishment of the call (for example the impulse transmission) do not become operative within a given time, are also used to release the connecting devices which haveabeen seized by rendering the calling condition at the calling line inoperative if the calling station delays in giving the clearing signal, i. e., does not replace his receiver within a given time after the termination of a call or after the operation of a signal indicating that the call in the desired direction cannot Ibe set up.

'I'he drawingl shows the arrangement in whichl the calling condition at the calling subscribers line is rendered inoperative if after the operation of the busy signal, which informs the calling -station that the connection cannot be established,

the clearing signal which, for example, may consist of the interruption of the feeding circuit, is not given within a given time.

The calling subscriber causes the ilrst group selector to be raised to that contact level over which calls in the desired trame direction are set up by dialing an impulse train. If all the outgoing lines are busy the group selectdr steps around in the known way and closes an overflow contact G Iw thereby connecting up the thermorelay Th2. The thermo-relay heats up and at the same time the calling` subscriber receivesvthe busy signal in any desired manner (not indicated).

If now the subscriber does not hang up within e the heating period of the thermo-relay Th2v the contact 62th2 is closed thereby preparing for the complete energization of the cut-off relay T over its winding II.- 'I'his circuit is completed when 5 the meter stepping device ZfS brings about the next influencing of the meter circuit by operating contacts lab, iab and 52ab.

'I'he eflect of the switching over of the metermg circuit of the calling une is that the cauing 10 condition at the subscribers line is rendered inoperative as already described and as a result the calling subscribers station canlexertl no influence on the connecting devices of the exchange. These are released' on account of the release of 15 relays VI, P2, A and B and are made ready toreceive other calls.

What is claimed is:v y 1. In a telephone system, a plurality of lines, switching apparatus having access to said lines,

another line, means for seizing said apparatus over said other line to extend a call over an idle vone of said plurality of lines. means in said apparatus for determining if an idle one of said plurality of lines is available, means for causing a signal to be reverted over the calling lineif all of said plurality of lines are engaged'. and

means in'said apparatus for initiating the release of said apparatus from said line a predetermined interval of time after said signalling -l if said apparatus is not previously released byA the abandonment of said call.

2. In a telephone system, automatic switching apparatus, a subscribers line having access thereto, a bridge normally across said line,a cut-off 85 relay individual to said line, means for operating said relay to open said bridge when saidY appa, ratus is taken into use over said line for the extension of a call, and means for again operating said cut-oft relay to thereby initiate the release 40 of said apparatus from said line.

3. In a telephone system, automatic switching apparatus, a subscribers line having accessl thereto, a bridge normally across said line, a cutofi relay individual to said line, means for operating said relay to open said bridge when said apparatus is taken into use over said line forthe extension of a call, means for controlling said apparatus over said line to extend said call, and means in said apparatus effective if it is not so 50 controlled within a predetermined interval lof time for again operating said cut-01T relay to thereby initiate the release of said apparatus from said line.

4. In a telephone system, automatic switching apparatus, a subscribers line having access thereto, a bridge normally across said line, a cut-off relay individual to said line, means for operating said relay to open said bridge when said apparatus is taken into use over said line for the extension of a call, means in said apparatus for causing a signal to be reverted over said subscribers line, and means effective if said apparatus is not released by the abandonment oi said call within a predetermined interval of time thereafter for again operating saidfcut-off relay to thereby initiate the release of said apparatus from said line. y

5. In a telephone-system, automatic switching apparatus, a subscribers line having access thereto, a bridge normally across said line, a cut-oil relay individual to said line, means for operating said relay to open said bridge when said t apparatus is taken into use over saidline for the extension of a call, means for transmitting signals to said apparatus over said line to cause a connection'` to be extended therefrom, and means in said apparatus for again operating said relay to initiate the release of ysaid apparatus from said line if, after the receipt of said signals, said connection is not so extended.

6. In a'telephone system, automatic switching apparatus, a subscribers line having access thereto, a two-step relay individual to said line, means for automatically taking said apparatus into use over said line responsive to a calling con-- dition thereon, means in said apparatus `for thereupon operating said relay a first step and for normally holding said relay so operated while said` apparatus is in use, means for operating said relay a second step to thereby cause said apparatus to be released from use, and means for holding said relay as last operated independently of said apparatus so long as the calling condition exists on the line. y

7. In a telephone system, automatic switching apparatus, a subscribers line having access thereto, a two-step relay individual to said line, means for automatically taking said apparatus into use over said line responsive to a calling condition thereon, means in said apparatus for thereupon operating said relay a first step and for normally holding said relay-so operated while said apparatus is in use, means for controlling said apparatus over said line to direct the extension of a call thereover, means in said apparatus if it is not so controlled within a predetermined interval of time for operating said relay a second step to thereby cause said apparatus to be released from use, and means for holding said relay as last operated independently of said apparatus so long as the calling condition exists on the line.

8. In a telephone system, automatic switch- 'ing apparatus, a subscribers line having access thereto, a two-step relay vindividual to said line, means for automatically taking said apparatus into use over said line responsive to a calling condition thereon, means in said apparatus for thereupon operating said relay a first step and for normally holding said relay so operated While said apparatus is in use, means in said apparatus for at times causing a signal to be reverted over said subscribers line, means eective if said apparatus is not released by the removal of said calling condition from said line within a predetermined interval of time thereafter, for operating said relay a second step to thereby cause said apparatus to be released from use, and means for holding said relay as last operated independently of said apparatus so long as the calling condition exists on the line.

9. In a telephone system, subscribers stations and lines therefor, switching apparatus having access to said lines, means for closing the line loop at any of said stations to initiate a call, means for causing said apparatus to search for the closed line loop of the calling station, a testing circuit completed over the closed line loop at said station to initiate seizure of said line, a relay individual to said line, and means for operating said relay to disconnect said circuit from said line responsive to said seizure.

10. In a telephone system, a subscribers station and a line therefor, automatic switching apparatus, means responsive to a calling condition upon said line for associating said apparatus with said line, a testing circuit completed over the closed line loop at the subscribers station responsive to the association of said apparatus with said line, a cut-E relay, means for seizing said line and for operating said relay responsive to the completion of said circuit, said relay effective 11. In a telephone system, a subscribers'sta-r tion and a line therefor, automatic switching apparatus, means responsiveto a calling condition upon said line for associating said apparatus with saidline, a vtesting circuit completed over the closed line loop at the subscribers station responsive to the association of said apparatus with said line, a cut-od' relay, means for seizing said lineand for operating said relay responsive to the completion of said circuit, said relay eiective tothereupon disconnect said testing circuit from said line, means for transmitting signals over ,said line to control said apparatus, and means in said apparatus effective if said signals are not received thereby within a predetermined time after said seizure for operating said relay again to thereby initiate the release of said apparatus from said line.

12. In a telephone system, a subscribers station and a line therefor, automatic switching apparatus, means responsive to a calling condition upon said line for associating said apparatus with said line, a testing circuit, completed over the closed line loop at the subscribers station responsive to the association of said apparatus with said line, a cut-off relay, means for seizing said line and for operating said relay responsive to the completion of said circuit, said relay effective to thereupon disconnect said testing circuit from said line, means for transmitting signais over said line to control the extension of a connection therefrom, and means in said apparatus effective if,l after said signals are received thereby, said connection is not so extended for operating said relay again to thereby initiate the release of said apparatus from said line.

13. In a telephone system, a subscribers station and a line therefor, automatic switching apparatus, means responsive to a calling condition upon said line for associating said apparatus with said line, a testing circuit completed over the closed line loop at the subscribers station responsive to the association of said apparatus with said line, a cut-off relay, means for seizing said line and for operating said relay responsive to the completion of said circuit, said relay effective to thereupon disconnect said testing circuit from said line, means in said apparatus for at times causing a signal to be reverted to the calling subscriber, and means effective if said apparatus is not released by the removal of said calling condition from said line. within a predetermined interval of time thereafter for operating said relay again to thereby initiate the release of said apparatus from said line.

14. In a telephone system, a subscribers stay responsive to the completion of said testing circuit to thereby cause said testing circuit to be disconnected from said line, another circuit for said relay, means for operating said relay its second step over said otherl circuit to cause said apparatus to be released from said line.

15. In a telephone system, a subscribers station and a line therefor, automatic switching apparatus, ymeans responsive to a calling condition upon said line for associating said apparatus with said line, a circuit completed over the closed line loop at the calling station responsive to the association of said apparatus with said line, a two-step relay associated with said line, a circuit for seizing said line and operating said relay its rst step responsive to the completion of said rst circuit to thereby cause said first circuit to be disconnected from 'said line and connected to said relay, and means in said apparatus for operating saidrelay a second step over said rst circuit to cause said apparatus to be released fromisaid line.

- 16. In a telephone system, a .subscribers station and a line therefor, automatic switching apparatus, means responsive to a calling condition upon sa-id line for associating said apparatus with said line, a circuit completed over theclosed line loop at the calling station responsive tothe association of said apparatus with said line, a

two-step relay associated with said line, a circuit for seizing said line and operating said relay its iirst step responsive to the completion of said iirst circuit to thereby cause said ilrst circuit to be disconnected from said line and connected to said relay, and means in said apparatus for operating said relay a second step over said iirst circuit to cause said relay to be disconnected from said second circuit and connected to said line, whereupon said apparatus is released from said line and said relay is maintained as last operated over said line asv long as the calling condition exists thereon.

17. In a telephone system, a plurality of sub `scribers lines, an automatic switch having .ac-

cess to said lines, a starting lcircuit for said switch normally connected to all of said lines, a marking circuit for said switch normally connected to one line, said circuits closed responsive to a calling condition on said one lineVsaid switch thereupon eiIective `to seize said line; -a' `single switching device individual to said one line, said device initially operated responsive t said seizure to thereby disconnect said starting circuit and said marking circuit from said line, means eiective at times for further operating said device to thereby cause said switch to be released from said line.

18. In a telephone system, subscribers sta-` tions and lines therefor, switching apparatus having access to said lines, a startingy circuit connected to all of said lines and completed by a calling condition on any one of said lines' to initiate the operation of sa'id apparatus, a testv ing circuit completed over the closed line loopvat the calling stationlwhen said apparatus is associated therewith, a two-step relay associated with said line, means for operatingsaid relay its rst step responsive to the completion of said' a line relay connected to said line and operated'.y responsive to a calling'condition thereupon, a

cut-off relay normally disconnected from the line operated thereafter to disconnect said lin'e relay from the line, and means for connecting said cut-oi relay to said line to maintain same operated thereover for the duration of said calling condition.

20. In' a telephone system, a plurality of, subscribers' lines, a linerelay connected in common to said lines' and operated responsive to a call-- ing condition upon any of said lines, a plurality of cut-oi relays each individual to one of the lines, means for operating the cut-oi relayassociatedwith the calling line to disconnect said line relay from that line, and means effective at' times to connect said cut-olf :relay to its associated line to maintain said cut-off relay operated thereover for the 'duration of said calling condition.

21. In a telephone system, a subscribers line.

switching apparatus associated with said line responsive to a rcalling condition thereupon, a relayindividual to said line operated responsive to the association of 'said apparatus therewith, means effective at times to connect said relay to said line to maintain same 'operated'thereover for the duration of said calling condition thereupon, and means for disassociating said apparatus from said line at said times.-

22. In a telephone system, a subscribers line. switchingapparatus associated with said line responsive to a calling condition thereupon, a relay individual to said line operated responsive to the` association oi said apparatus therewith, means in said apparatus controllable over said line by the subscriber, means effective if the control over said means is Inot exercised by the subscriber Within a certain lengthoftime both to connect said relay to said line to maintain FRIEDRICH LILL. l 

